Renal failure is a frequent complication of septicemia that contributes significantly to mortality, particularly in postoperative patients in the ICU. In the U.S. septicemia is the 12th leading cause of death in adults and the 9th leading cause of death in children 1-4 years of age. Current therapy is, for the most part, only supportive. Thus, the long-term objective of our research is to identify new therapeutic targets to treat sepsis-induced renal injury. In this proposal, we will describe a functional defect in the kidney that may represent a previously unrecognized vascular pathway involved in polymicrobial sepsis- induced renal injury using the most clinically relevant murine model, cecal ligation and puncture (CLP). Our preliminary data show that inhibition of inducible nitric oxide synthase, inhibition of caspases, or inhibition of p53 each can prevent CLP-induced renal failure in mice. We also discovered a dramatic loss in perfused cortical peritubular capillaries following CLP that is ameliorated by these three classes of inhibitors. This unexpected and novel finding of a CLP-induced vascular defect mediated by reactive nitrogen species (RNS), caspases, and p53 is the basis of our central hypothesis that in sepsis, RNS-initiated activation of caspases results in a decline in peritubular capillary perfusion that leads to RNS-dependent tubular epithelial injury and ultimately renal failure. We will use biochemical and intravital videomicroscopy techniques to assess peritubular capillary dysfunction and tubular injury following mild and severe CLP in mice. Aim 1 will determine if peritubular endothelial injury and capillary dysfunction are early events that precede tubule epithelial cell injury. Aim 2 will determine the relative contributions of caspase-3 and p53 in peritubular capillary dysfunction and tubule epithelial cell injury using both pharmacological and genetic approaches. Aim 3 will determine if RNS-induced activation of p53 and caspases contribute to CLP-induced peritubular capillary dysfunction and tubule epithelial cell injury using pharmacological a genetic approaches. Both Aim 2 and Aim 3 will use in vivo studies as well as complementary in vitro studies with primary cultures of renal endothelial and tubular epithelial cells. PUBLIC HEALTH RELEVANCE: These studies will supply valuable information on the cascade of signaling and cell- specific events that result in sepsis-induced renal injury. They will identify new signaling pathways and test them as new therapeutic targets for this devastating disease.